Switch-stack assembly



March 24,1942. C, |V|NGSTON I I 2,277,443

swITcHsTAcK ASSEMBLY Filed May 10, 1941 la7@ Uem Patented Mar. V2 4, 41942 OFFICE A 2,217,443 swrrcn-s'racx ASSEMBLY canard mvlmton, calmo, nl., minor te Gomar- Electrio Co., Chicago, lll.

Application May 10, 19,41, Serial No. 392,857

3Claims.

This invention relates to a switch stack assembly of the type consisting of a plurality oi elongated spring leaf switch blades secured` at one end-between insulating pieces or wafers arranged in a stack with the'switch blades sandwiched in between alternate insulating pieces. This kind or switch is sometimes referred to as a jack switch.

The principal object of the invention is the provision oi means for automatically taking up any shrinkage or looseness between the insulating wafers whereby to prevent looseness of the switch blades mounted therebetween and consequent inaccuracy of alignment between the contact point on the switch blades, or faulty electrical contacting between such contact points when one or more oi the blades is operated in switching movement.

Since the stack ci insulators with the switch blades secured therebetween is usually mounted by means ci one or more screws passing through the entire assembly oi wafers and switch blades,- it is necessary to yemploy an insulating sleeve around the mounting screw or screws to prevent short-circuiting the portions of the switch blades through which these screws pass, and-it irequently happens that owing to slight variations in the thickness of the insulating wafers or in the length of insulating sleeve cuts, the end'portions of said sleeves may protrude slightly above the stack of insulating wafersthat is above the switch stack assembly, and trouble is at once encountered because the mounting screws cannot be turned up tightly against the stack of insulating wafers, but instead, the screw bears against the protruding portion of the sleeve, wltha consequent looseness of the switch stack assembly.

A further important object of theinventlon is therefore to provide in addition to the aforesaid automatic take-up means for shrinkage and the like, a means for obviating the diillculties arising from slight variations in dimension o! the wafers and the sleeves.

A furtherand important object of the invention is provision in a switch stack assembly, of a resilient header member which will bear down against a plurality of points on the topmost insulating wafer of the switch stack; which will automatically compensate for any looseness between the wafers of the switch stack due to shrinkage and the like; and which will also permit the application o! adequate pressure on the switch stack by the mounting screws notwithstanding the fact that the insulating sleeves for the mounting screws may protrude slightly above r the top level of the stack due to various kinds of inaccuracy in dimension.

Other objects and novel aspects of the invention reside in details of construction and operation oi the preferred embodiment now to be described' in view of the annexed drawing, in which:

Fig. 1 is a partially exploded perspective of the novel switch stack assembly;

Fig. 2 is a transverse section through the switch stack assembly, showing a protruding insulating sleeve;

Fig. 3 is another transverse section through the switch stack showing the action of the spring header with a properly dimensioned sleeve; A

Fig. e is an enlarged perspective o! the im-A t proved spring header and take-up member shown in the preceding gure;

For purposes of illustration, a conventional type ol jack switch is shown in Fig. l, and is there mounted on a metal mounting shell or member Si, the switch including a plurality of elongated leaf spring blades II) and Il mounted at one end between alternate insulating blocks yor wafers The mounting ends of these switch blades are provided with one or more holes, corresponding to similarly located holes in each`r of the wafers i3, through which are passed tubular insulating sleevesrll' of liber or the like, including hard rubber.

The blades and insulating wafers I3 constitute a switch stack assembly, and in order to hold the same in assembled relation upon the shelf 8, there are provided one or more mounting screws i4 adapted to pass through the sleeves I2 and thread into the mounting member or shelf il (see Figs. 2 and 3 also). 'I'he sleeves I2 prevent the screws Il from making'electrical contacts with any portion of the blades Ill, thereby to prevent short circuits between the blade elements, it being understood that in the simple switch structure shown inr Fig. 1 only two switch blades are shown, whereas in practice it is customary to use a larger number of such switch blades.

In Fig, there is shown to exaggerated scale a portion I2a of one of the insulating sleeves projecting above the uppermost insulating wafer I3a, and it will be apparent that if the mounting screw I6 were turned down tightly (without the intermediary of any kind of washer or take-up device) the'head of the screw would bear against the end of the protruding portion I2a and would exert no pressure whatever against the topmost wafer ISa of the assembly. Obviously under such conditions the switch stack assembly would be loose and would be wholly unsatisfactory from an electrical or mechanical standpoint for use as a switch, as will be readily recognized by those skilled in the art since it is imperative that the switch blades I0 and II be accurately aligned and permanently amxed in order that they may engage and disengage accurately and promptly and firmly in making and breaking electrical circuits.

In practice it has been found impossible, from an economical production standpoint to prevent variations in dimensions either Vof the wafers I3 or in the length of the sleeve I2, and it is therefore a very commonly encountered difficulty in the manufacture of such switch stacks to find either imperfectly secured assemblies, or to be faced with the necessity for rejecting the imperfectly fitting sleeve, thus increasing the manufacturing costs (which must be closely calculated on such a small item).

The invention provides means in the nature of a spring header element generally indicated at Il, Figs. 1 and 4, and which is in the preferred shape of a rectangle of spring metal bowed transversely to provide an arcuate conformation as indicated at lib in Fig. 4. One or more holes Ila are provided to receive the mounting screws Il in alignment with sleeve portions I2.

` As a general rule the protruding sleeve portions I2a (Fig, 2) generally do not extend more than two or three-thousandths of an inch above the surface of the top wafer I3a, although the showing in Fig. 2 is considerably exaggerated in order to bring out the nature of the diiliculty which the present invention overcomes.

Therefore, the degree to which the header members I5 are bowed or sprung in giving them the aforesaid arcuate conformation, need only be sumcient to give a springing range of about fifty-thousandths o'f an inch down to approximately zero thousandths, when the header member would be substantially at, corresponding to a perfectly flush sleeve end I 2a. In practice it is not necessary to drive the header member I5 down flat even though the sleeve may nt perfectly as illustrated in Fig. 3, wherein the degree of arcuateness or bowing left in the header member Il is more than would exist in practice, the bowing indicated at lib being exaggerated for purposes of clarity of illustration. Actually the header member I5 would be flattened out considerably more than shown in Fig. 3.

The important thing in the action of the header member Il is that all along the opposite parallel edge portions ISc (Figs. 2 and 3), there be substantial bearing pressure against the upper surface4 of the top insulating wafer I3a, even when there be a protruding portion I2a of the sleeve.

It will be apparent from an examination of Fig. 4, for'example, that the improved header member I5 may be very inexpensively manufactured bya stamping or punching process, and yet the general annoyance and potential increase in manufacturing costs of switch stack assemblies is completely obviated by the use of such a means. Moreover, the general operating stability of the switch stack is improved throughout its useful life b'eause shrinkage or settling of the insulating wafer elements I3, which would otherwise cause a loosening up of the switch blades, is automatically compensated for by the constant pressure exerted by the header member, and this would be true whether the shrinkage or looseness in fit were to result from a slow aging of the insulating material itself. or from more abrupt and frequent variations in expansion and contraction due to temperature changes, it being pointed out that switches of this type are commonly used in mechanisms which cause frequent changes in temperature in the immediately surrounding air, and unless the switch stack can be rmly secured in position, such variations are a sure cause of future trouble.

It will be recognized that the shape and conformation of the header member may be altered to suit the peculiarities lor requirements of a given switch stack assembly or other adaptation, and the invention is therefore no't to be limited to speciilc details of shape, form or location or application, except as may be necessarily imported by the appended claims.

Having thus described 'my invention, what I claim as new and desire to protect by Letters Patent of the United States is:

l. In combination with a switch stack assembly of the class described, an accommodation header comprising a piece of spring metal bowed to provide a concavo-convex configuration, and provided with one or more holes for passage of a mounting screw or the like extending into said assembly, said header being adapted for mounting on the topmost member of the stack: with its concavity facing said member and edgewise portions bearing by urgence of said screw against the stack with space available in the concavity for accommodation of protruding portions of the stack, substantially as set forth.

2. In a switch stack assembly of the type including one or more elongated spring switch blades mounted between two or more insulating members, and lsecured to a mounting member by means of one or more screws passed through said blade or blades and said insulating members and surrounded by an insulating sleeve likewise passing through said blade or blades and insulating members, the combination of a header means adapted to automatically take up looseness between said insulating members and blades and to compensate for ordinary oversize in tolerance in the length of the said sleeve, said means comprising a header member constructed of spring metal or analogous material of substantially rectangular form and bowed transversely with openings therethrough to accommodate mounting screws passing through said sleeve, said header being adapted to overlie the topmost insulating member and to have edge portions pressed against said member by tightening up of said mounting screw or screws with any protruding portion of the sleeve as aforesaid extending into the space beneath the bowed portion of the header immediately surrounding said screw or screws,

3. A switch stack assembly, comprising, in combination, a plurality of switch blades, secured between alternately positioned insulating wafers arranged in a stack, there being one or more insulating sleeves passed through said blades and wafers in said stack to provide a protective passage for a mounting screw, said stack being adapted for mounting on a support by means of screws passed through said sleeves, together with a header member in the form of an elongated piece of metal bowed transversely of its length and provided with mounting holes for alignment with said sleeves, said screws being passed through said mounting holes into said sleeves and turned up against said header to spring the latter against the topmost insulating wafer in said stack, whereby to provide a concavity between the underside of the header and said topmost wafer and to cause edgewise portions of the header to bear against the latter when said screw is turned up, and to provide a space to accommodate oversize in length of said sleeves.

CALLARD LIVINGSTON.

IDISCLAHvIErz 2,277,443.'Callard Livingston, Chicago, Ill. SWITCH-STACK ASSEMBLY. Patent dated March 24, 1942. Disclaimer filed September 3, 1942, by the inventor, and the assignee, Oomar Electric Company;

Hereby limit claims 1, 2, and 3 of said patent to that form of header which is ooncaVo-convex and in which the eurvatures of concavity and convcxity are substantially uniform and not interrupted by flat surfaces; that form of header which is rectangular' and provided with a central flat arca with marginal portions sloping downwardly and outwardly from said flat area and either partially or totally surrounding said flat area, being specifically disolaimed hereby.

[Oficial Gazette October 13, 1942.]

DISCLAIMER 2,277,443.'-Oallard Livingston, Chicago, Ill. SWITCH-STACK ASSEMBLY. Patent dated March 24, 1942. Disclaimer filed September 3, 1942, by the inventor, and thc assignee, Comar Electric Company;

Hercby limit claims 1, 2, and 3 of said patent to that form of header which is concavo-convcx and in which the curvatures of concavity and convoxity arc substantially uniform and not interrupted by flat surfaces; that form of header which is rectangular and provided with a central iat arca with marginal portions sloping downwardly and outwardly from said flat area and either partially or totally su rrounding said flat arca, being specifically disclaimed hereby.

[Oficial Gazettev October 13, 1942.] 

